The present invention is directed to a heat sink and an electronic circuit module including the same. More particularly, the present invention is directed to a heat sink having wire mesh fins or a plurality of pins and horizontal wires for heat dissipation.
Microprocessors and other electronic circuit components are becoming more and more powerful with increasing capabilities, resulting in increasing amounts of heat generated from these components. Packaged units and integrated circuit die sizes of these components are decreasing or remaining the same, which increases the amount of heat energy given off by the components for a given unit of surface area. Furthermore, as computer related equipment becomes more powerful, more and more components are being placed inside the equipment, which is also decreasing in size, resulting in additional heat generation in a smaller volume of space. Increased temperatures can potentially damage the components of the equipment, or reduce the lifetime of the individual components and the equipment. Therefore, large amounts of heat produced by many such integrated circuits must be dissipated, and therefore must be accounted for in designing the integrated circuit mounting and packaging devices.
Electronic components can be attached to a heat sink in order to dissipate heat from the components. One type of heat sink that may be used is a parallel plate heat sink, such as that shown in FIGS. 1A and 1B. As shown in FIGS. 1A and 1B, such a heat sink includes a thermally conductive base 10 and fins 12. The fins 12 have generally planar, parallel major surfaces and are arranged generally parallel to one another. Cooling air, blown by a cooling fan, not shown, can flow in gaps or spaces between the plates either in a direction parallel to the base 10 or perpendicular thereto.
Another type of heat sink is shown in FIGS. 2A-2C. The heat sink shown in FIGS. 2A-2C is similar to that shown in FIGS. 1A and 1B, and includes a thermally conductive base 10 and fins 12xe2x80x2. The fins 12xe2x80x2 in the heat sink shown in FIGS. 2A-2C are made of, e.g., a single piece of thermally conductive material folded to provide a plurality of parallel fins 12xe2x80x2.
The overall size of the heat sinks is limited by the volume constraints of the housing. To improve the amount of heat dissipated from the heat producing components, there is a need to increase the surface area of the heat sinks without increasing the volume of the heat sinks. One technique to increase surface area is to reduce the spacing between fins of the heat sink to increase the surface area of the heat sink. However, this results in tighter spacing between fins, which in turn increases air flow resistance resulting in higher thermal resistance.
U.S. Pat. No. 6,269,864 accomplishes an increased surface area by, in one embodiment, having a thermally conductive base including a plurality of fin structures extending upwardly from the thermally conductive base, the plurality of fin structures having a plurality of surface area enhancer structures extending outwardly from a first surface of the plurality of fin structures to increase a convection surface area of the heat sink for a given volume.
In parallel plate type heat sinks, as cooling fluid, e.g., air, is blown between the plates, a laminar or turbulent boundary layer forms along the surface of the plate. Lacking an efficient heat transfer mechanism, the speed and power capabilities of the electronic circuit modules are severely limited. The parallel plates or folded fins type systems allow the development of thick boundary layers, and thus higher thermal resistance. Although narrow channel heat sinks significantly improve heat dissipation, they, like other plate fin designs, suffer from boundary layer formation. The boundary layer consists of hydrodynamic and thermal layers, which result from friction or drag between cooling fluid and a plate fin. The layer tends to blanket the plate fin thereby insulating it from the cooler fluid flow. Thus reduces heat transfer. Additionally, the layer narrows the remaining channel available to fluid flow, which further impedes fluid flow thereby compounding the problem. The boundary layer therefore thickens as the fluid progresses down the channel contributing to high pressure within the fin field.
To reduce boundary layer formation in heat exchangers, it is possible include irregularities such as protrusions, indentations and louvers along the plate fin surface. These irregularities are intended to disturb the boundary layer to prevent it from building up. From the standpoint of boundary layer disruption, the greatest improvement would be a device having as many irregularities as possible. Unfortunately, however, such an approach leads to practical problems. Extrusion techniques are limited to producing lengthwise ridges (horizontal and vertical), which have limited ability to disrupt the boundary layer. Other manufacturing techniques such as casting and machining also preclude intricate plate fin textures. Perhaps more importantly though, increasing irregularities, as described above, also decreases the velocity of the passing fluid within the channels formed by the textured plate fins which tends to increase the pressure drop through the fin field.